Ensuring High Availability of Web Applications in Windows Azure

To prevent your Windows Azure applications from potentially experiencing a loss of availability during platform upgrades, we recommend deploying more than one instance of your web-facing roles. Doing so also enforces the Windows Azure Compute Service Level Agreement (SLA), which guarantees 99.95% external connectivity for Internet-facing roles when two or more role instances are deployed for a given application. Please click here to download the full Windows Azure Compute SLA.